One of the coolest thing I have ever seen in the MTG Olschool community is the Gentlement's agreement.
The first time I ever heard of it was in Magus report of WSK 2015. In short, Magus and Åland entered an agreement where each party would remove the two fun-killers card in Oldschool, namely Library of Alexandria and MindTwist, from their respective decks before starting the duel.
What a warm feelling it was to see other players being sensible to the initiative with Legion Urborg even building upon it into "True gentlemnism".
And now there is even a Facebook group you can join, and a pin(source)!
In a Gentlemen‘s game, we exclude or exchange Mind Twist and Library from our Decks. Really true Gentlemen do not even include the card in their tournament Deck.
We as Gentlemen do not judge any non-Gentlemen for "not being a Gentlemen“. We try to explain what we do but if anyone refuses, its fine.
We like to play more "casual" than competitive – but always with a kind of competitive edge (it makes most of the time no sense to e.g. exclude Power just for the sake of "more oldschoolness"). Sometimes also a Gentlemen can build a Spicy Tier 1 Deck – its not a crime.
We love the game and also love to actually play Magic – therefore it is absolutely common (but not written in stone) that a Gentlemen grants any opponent multiple mulligans to 6 rather than letting the opponent going down to 5, 4, 3, etc.
We want to celebrate our matches in a friendly and warm enviroment – it is absolutely common to give the other player hints about possible next actions ("please be aware, i have an untapped Mishra‘s factory which i can pump to 3/3“ or "yes you can take that action back“ etc.)